The present invention relates to an ink jet device comprising a number of ink channels that are arranged side by side and are covered by a flexible sheet, and a corresponding number of actuators that are arranged to exert an actuating force onto the sheet through a bump having a surface facing the actuator and a surface facing the sheet, wherein the bumps are formed on the sheet in such an orientation that the surface facing the actuator has an area larger than the area of the surface facing the sheet and the bumps are bonded to the actuators by means of an adhesive. The present invention further relates to a method of manufacturing such an ink jet device.
JP 2003039669A discloses an ink jet device of the type indicated above, wherein the bumps have a T-shaped cross-section.
JP 7-276 626 A discloses an ink jet device wherein the ink channels, the flexible sheet and the bumps are formed by etching a silicon substrate. The bumps have a trapezoidal cross-section, the larger base of which is facing the sheet, so that the bump tapers towards the actuator.
EP 0 820 869 A1 discloses an ink jet device wherein the ink channels are formed in a channel plate on which the flexible sheet is superimposed as a separate member. The sheet is formed with an array of parallel grooves, so that ridges formed between the adjacent grooves serve as bumps that project towards the actuators. The grooves have a half-circular cross-section, so that the bumps have arcuate flanks and taper towards the actuators. The actuators are formed by piezoelectric fingers, and the tip end of each finger is bonded to an associated one of the bumps by means of an adhesive. Each ink channel is connected to a nozzle through which an ink droplet is to be jetted out. In order to create an ink droplet that is expelled from the nozzle, the piezoelectric actuator is at first energized to perform a contraction stroke, so that the portion of the flexible sheet covering the associated ink channel is drawn away from the ink channel. As a result, the volume of the ink channel increases and a corresponding amount of ink is sucked in from an ink supply system. Then, the actuator is energized with an opposite polarity, so that it performs an expansion stroke and deflects the sheet into the ink channel. In this way, an acoustic pressure wave is generated in the ink channel, and this pressure wave propagates towards the nozzle and causes an ink droplet to be expelled.
A general problem that is encountered in conjunction with ink jet devices of this type is the so-called cross-talk phenomenon. This means that the process of droplet generation in one channel also influences the ink in the neighbouring channels and therefore disturbs the drop generation processes in the neighbouring channels. One of the reasons is that the deflections of the sheet cannot strictly be confined to an individual ink channel but are accompanied by slight deflections of those portions of the sheet that cover the neighboring channels.